Roll Dart SDK from 4b7b565eb468 to 91cbf6d7563a (1 revision) (#173469)

https://dart.googlesource.com/sdk.git/+log/4b7b565eb468..91cbf6d7563a

2025-08-08 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.10.0-80.0.dev

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-sdk-flutter
Please CC codefu@google.com,dart-vm-team@google.com on the revert to
ensure that a human
is aware of the problem.

To file a bug in Flutter:
https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Author: engine-flutter-autoroll

DEPS

@@ -56,7 +56,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '4b7b565eb4686d534da6f3e8e758a9d74cf5998e',
+  'dart_revision': '91cbf6d7563a19d379096cc7771275812a4a2c5f',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py